. Cell heredity. Cytogenetics. HEREDITY IN SOMATIC CELLS 373 methylcholaiithrciu' do not grow when transplanted haek into the parental lines but do so onlv when transplanted into the hybrid line. This is beeaiise eaeh parent was homozygous for either the H-2 or the H-2' allele, while the hvbrid was a heterozygote, H-2"/H-2'. Therefore, the tumor elieited antibodies in the parental hosts which lacked one or the other gene and the corresponding antigen. But sometimes variant cells arise in the tumors, allowing sur\i\al in one of the parental hosts; their frequency is increased by X-rays. Se
. Cell heredity. Cytogenetics. HEREDITY IN SOMATIC CELLS 373 methylcholaiithrciu' do not grow when transplanted haek into the parental lines but do so onlv when transplanted into the hybrid line. This is beeaiise eaeh parent was homozygous for either the H-2 or the H-2' allele, while the hvbrid was a heterozygote, H-2"/H-2'. Therefore, the tumor elieited antibodies in the parental hosts which lacked one or the other gene and the corresponding antigen. But sometimes variant cells arise in the tumors, allowing sur\i\al in one of the parental hosts; their frequency is increased by X-rays. Serological tests indicated that some of these variant tumors had lost the H-2" antigen, allowing them to grow in the H-2''/H-2'' parent (Figure ). In model experiments in\'ol\ing the artificial of compatible and incompatible tumor cells, it was shown that the compatible cells had an absolute selective advantage and grew even when present in proportions as small as 4 X 10"', despite the destruction of their incompatible neighbors. As a con- sequence, variation and selection seem the explanation. Variation in the constitution of tumors is of common occurrence; usuallv their antigens are only a sample of those in the cells that produced them. It is not at all sure that point mutations are the basis; chromosomal changes seem usually involved, especially when there is a great increase in the range of transplantabilitv. But e\en when specific variants arise from controlled heterozygotes, deletions, somatic crossing over, and other mechanisms are a priori as probable as point mutation. Parent a H-2°/H-2° Transplant takes _ Parent s H-2'/H-2' /I / I \ \ Hybrid / / / \ H-2''/H-2' \ / \ / ^ y V ^ _ ^ ^^ — — Transplant Transplant fails fails Somatic vari< ation. Transplant fails FIGURE Diagram of the consequence of somatic variation in a heterozygous Please note that these images are extracted from scanned page images that may have been digital
Size: 2184px × 1144px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiodiv, bookpublishernewyorkwiley
